the signficance of the process of mound building is that it is a lot like pyrimids but they are built with a flat top instead of a point (us history e2020)
The first known inhabitants of modern-day United States territory are believed to have arrived over a period of several thousand years beginning sometime prior to 15,000 - 50,000 years ago by crossing Beringia into Alaska.[2] [3] Solid evidence of these cultures settling in what would become the US is dated to at least 14,000 years ago.[4]